It seems to me that the purpose of an index is to point the reader to information not to give information. Therefore, I find it simple and space saving to put all entries under the birth name and under the other names simply say see xxx.

For example
Jones, Mary pp 5,30,88,56.
Smith, Mary see Jones, Mary

In the case of two people with the same name
Jones, Mary (daughter of Philip and Jessie) pp 19,59,65,99.
Jones, Mary (daughter of Elias and Eleanor) pp 50,55.
Doe, Mary see Jones, Mary (daughter of Phillip and Jessie)

In a biography the various Mary Jones would be identified in the index with the relationship to the subject.

If the text does not make relationship clear the author has not done his job.